1. Field of the Invention
The invention is directed to an improved fastening device for a fuel injection valve in a bore in the cylinder head of an internal combustion engine.
2. Description of the Prior Art
One fastening device of the type with which this invention is concerned is known for instance from German Patent DE 195 21 363 C1. In the fastening device shown there, a fuel injection valve is fastened in a bore in the cylinder head of an internal combustion engine, and the fuel injection valve, which has a longitudinal axis, is secured with a clamping jaw. The clamping jaw has a support face, with which it rests on a support point of the fuel injection valve. The clamping jaw is acted upon in its center by a fastening force, and the fastening force is exerted by a screw that presses the clamping jaw against the cylinder head. By means of the fastening force, the clamping jaw is pressed with its support face against the support point of the fuel injection valve and presses the fuel injection valve into the bore in the cylinder head. In DE 19521 363 C1, the support face of the clamping jaw is embodied in ball form and rests on a flat support point of the fuel injection valve. Care is taken here that the point where the clamping jaw rests on the support point of the fuel injection valve is oriented precisely in the direction of the longitudinal axis of the fuel injection valve, so that the fastening force will not cause any tilting moment on the fuel injection valve. However, this cannot always be reliably prevented in the construction shown there: Thermal expansion of the clamping jaw or other parts of the engine, or shaking or shifting, can cause the support face of the clamping jaw to shift on the fuel injection valve, so that the contact pressure is no longer introduced precisely centrally into the fuel injection valve in the direction of the longitudinal axis. The result can be a tilting moment of the fuel injection valve in the bore and hence an uneven mechanical load, which can impair the function of the moving parts in the fuel injection valve considerably.
A similar fastening device is known from U.S. Pat. No. 6,196,194. The clamping jaw shown there also has a ball-like shape on its support face and is embodied as forked, so that it engages two support points of the fuel injection valve which are diametrically opposed to one another. The fastening force is introduced here not in the center of the clamping jaw but rather at the end of the clamping jaw opposite the support face, and the clamping screw pushes the clamping jaw away from the cylinder head. The contact pressure is attained via an abutment on which the clamping jaw rests in its center region. This fastening device likewise has the disadvantage that the contact pressure does not always act centrally on the fuel injection valve, so that as already described, a tilting moment on the fuel injection valve can occur, with the attendant disadvantages.
The fastening device of the invention for a fuel injection valve has the advantage that the fastening force is always exerted symmetrically on the fuel injection valve, so that the fastening device does not exert any tilting moment, or at most only a very slight tilting moment. To that end, a support point is embodied on the fuel injection valve and forms a straight line, which is located in the same plane as the longitudinal axis of the fuel injection valve. As a result, the fastening force is introduced into a plane of symmetry of the fuel injection valve. The clamping jaw has a support face, which in the event of a horizontal shift, that is, perpendicular to the longitudinal axis of the fuel injection valve, slides across the support point, so that the point where the fastening force is introduced into the fuel injection valve remains fixed.
In an advantageous feature of the subject of the invention, the support face on the clamping jaw is embodied in planar form, so that it can easily slide along the linear support point of the fuel injection valve.
In a further advantageous feature, the clamping jaw is embodied as a two-armed lever, on one end of which the support face is embodied and the other end of which rests at least indirectly on the cylinder head, and the fastening force is introduced between the two ends of the clamping jaw. As a result of this embodiment, the already known clamping jaw can be used for the fastening device of the invention, with a slight modification of the support face.
In an advantageous feature, the linear support point on the fuel injection valve is a ridge which is formed by two chamfers. As a result of this embodiment, the linear support point can be manufactured simply.
In another advantageous feature, two support points diametrically opposed to one another relative to the longitudinal axis are embodied on the fuel injection valve, each embodied as a ridge formed by two chamfers. As a result, the fastening force can be introduced symmetrically on two sides of the fuel injection valve. This is especially advantageous if, on the end where the support face is located, the clamping jaw is embodied as forked.
In a further advantageous feature, the support point on the fuel injection valve is embodied as a jacket line of a support cylinder, whose longitudinal axis intersects the longitudinal axis of the fuel injection valve. This has the advantage that the clamping jaw, if it shifts horizontally, rolls with its support face over the cylinder and thus cannot exert any horizontal forces on the fuel injection valve. As a result, any tilting moments on the fuel injection valve that still occur are reduced still further. It can also advantageously be provided that two support cylinders be disposed coaxially in line with one another, each on one side of the fuel injection valve.